Smoke generator

ABSTRACT

A smoke generator for engines exhausting hot gases including an exhaust duct having a plurality of smoke-producing fluidinjection means mounted internally and circumferentially the duct and a plurality of baffle means extending longitudinally the duct between said injection means to channel the smoke and minimize turbulence within the duct.

United tates atent inventors Henry 0. Nelson San Diego; Howard F. King, La Mesa; Louis D. Dale, Bonita, all of Calif. Appl. No. 866,537 Filed Oct. 15, 1969 Patented Jan. 4, 1972 Assignee The United States of America as represented by the Secretary of the Army SMOKE GENERATOR 9 Claims, 6 Drawing Figs.

US. Cl 244/136, 40/21 3 Int. Cl 864d 1/00 Field of Search 244/136;

[56] References Cited UNITED STATES PATENTS 2,404,812 7/1946 Rankin 40/213 3,436,020 4/1969 Duthlon et al. 239/265.l7 X 1,514,106 11/1924 Savage 40/213 2,836,567 5/1958 Revre et a1 252/359.1 CG FOREIGN PATENTS 304,593 1/1933 ltaly 244/136 Primary ExaminerMilton Buchler Assistant Examiner-Gregory W. O'Connor Attorneys-J. C. Warfield, Jr., George J. Rubens and John W.

McLaren ABSTRACT: A smoke generator for engines exhausting hot gases including an exhaust duct having a plurality of smokeproducing fluid-injection means mounted internally and circumferentially the duct and a plurality of baffle means extending longitudinally the duct between said injection means to channel the smoke and minimize turbulence within the duct.

T R 47 ou BOA 0 PATENTEDJAN 41912 3.632.067

SHEET 1 OF 2 47 OUTBOARD INVENTORS HENRY 0. NELSON HOWARD E KING Y LOU/5 0. 041.5

wk. Qv/(m/ A TTORNEYS mzmcnm 4572 316321067 SHEET 2 BF 2 FIG. 6

' INVENTORS HENRY 0. NELSON HOWARD E KING wu/s 0. 041.5

ATTORNEYS SMOKE GENERATOR STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention relates to a smoke generator and more particularly to a smoke generator for use on engines having a hot exhaust gas that will produce a larger volume and greater density of smoke.

The use of smoke-producing apparatus for various types of vehicles and for different types of applications has been long established. Land operated smoke generators, especially the ones that are stationary, do not present a problem because of the unlimited storage facilities of smoke-producing fluid and size is no limitation. However, smoke-producing apparatus for use in aircraft for military purposes present limitations in the supply of fluid that can be carried and the weight and size of the apparatus. Therefore, the importance of obtaining a larger and denser volume of smoke with a lightweight smoke generator is of paramount military importance.

The prior art smoke generators for the most part, such as Levey et al., U.S. Pat. No. 2,422,024, are concerned with exhaust flow emanating from diesel engines which have a small diameter exhaust pipe. A single nozzle ejects the smokeproducing fluid into the exhaust pipe and a limited volume of smoke is produced. In addition, the smoke travels in a random and turbulent flow through the exhaust pipe which could cause a back pressure on the engine before being discharged.

SUMMARY OF THE INVENTION The novel smoke-generating system of this invention is for use on a prime mover developing hot exhaust gases that are used to vaporize the smoke-inducing medium. The system includes a generator unit that can utilize the exhaust duct of a reaction type thrust engine or provide its own enlarged duct through which the hot exhaust gases from any other type of engine may be vented. The smoke-generating system provides a source of pressurized smoke-producing medium, such as a liquid, which is injected into the exhaust duct at a plurality of spaced stations around the inner periphery. An important feature is the employment of bafile means between the injection stations to provide separate channels through which the smoke flows without turbulence between channels. The baffle means are preferably plates, which may extend to the center of the duct, and provide additional hot surfaces within the exhaust duct for vaporizing the smoke-producing liquid. A unique arrangement of piping provides a preheat path as well as avoiding the formation of holes in the duct.

STATEMENT OF THE OBJECTS OF THE INVENTION An important object of this invention is to provide a smokegenerating system which will produce a greater volume and higher density smoke flow.

Another important object is to provide a smoke generator which can be adapted to various types of engines and, a corollary object is to provide a generator of lightweight construction suitable for use on aircraft, such as helicopters.

Still another important object is to provide a smoke generator with baffle means that will produce nonturbulent flow.

A further object is to provide a smoke generator which will have a greater heated surface area for generating the smoke without adversely affecting engine performance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a H-3 type helicopter illustrated in phantom with part of the fuselage broken away to show the general arrangement of the novel smoke generator assembly;

FIG. 2 is a top plan view of FIG. I;

FIG. 3 is an enlarged perspective view of the smoke generator unit and piping arrangement;

FIG. 4 is an end elevation view of the exhaust end of the smoke generator of FIG. 3;

FIG. 5 is a longitudinal section taken along line V--V of FIG. 4; and

FIG. 6 is a perspective view of a modified smoke generator unit taken from an inboard position having a different arrangement of baffles and manifold.

Referring to the drawings where like reference numerals refer to similar parts throughout the figures, there is illustrated in FIGS. 1 and 2 a helicopter 10, having a Navy designation H-3, shown in phantom lines being representative of one type of vehicle on which the novel smoke generator system 12 can be employed.

Smoke generator system 12 generally comprises a smoke generator unit 14 which maybe connected directly or indirectly to a tailpipe 16 through which is discharged the hot gases of an engine 18. This type helicopter has two engines, being Navy designated T-58 turbo jets, disposed in side-byside relation, each engine having its own tailpipe and a novel smoke generator unit 14 associated therewith. It is obvious that the novel smoke-generating system of this invention may be utilized on other type engines and vehicles to meet prescribed operational requirements.

Each smoke generator 14, the details of which will be later described with reference to FIGS. 3-6, is fed a smoke-producing medium, such as a liquid, through a line 19 from a tank 20 located on a corresponding side of the aircraft. Both tanks 20 are pressurized by a common air pressure supply tank 22 through a pair of lines 24 and a pressure regulator 26 whereby the pressure in tank 22 of 1,800 p.s.i. is reduced to 18 p.s.i. found suitable in the described embodiment for transferring the smoke-producing liquid from tank 20 to smoke generator 14. A control valve 28 is provided in line 24 to control the regulated pressure to the supply tanks and incorporates means of relieving the tank pressure by an overboard vent to permit immediate shutoff of the smoke for any reason.

The smoke-generating medium must meet certain requirements, for example, it must produce a smoke of adequate opacity; require no special handling or storage precautions; be relatively inexpensive; be stable for extended periods; and have a sufficiently high flash point to avoid ignition. The following liquids are available that meet these criteria,

Diesel fuelNavy spec MIL-F-I 6884 Lubricating oil-Navy spec MIL-L-6081 Light turbine oil-Navy spec MILL-l 7672 Various mixtures of the above-described liquids were tried on the T-58 engine having an exhaust gas temperature of about 900 F. The best results were obtained using a 4060 percent proportion of diesel fuel with the remainder being either the lubricating oil or the light turbine oil.

An import feature of the smoke generator system is the absence of filters or critical orifices so that all smoke-generating fluids can be used successively even though they may be grossly contaminated with water, rust, metal particles, etc.

Smoke generator unit 14 to which the fluid is piped for generating the smoke is shown in detail in FIGS. 3-5, inclusive. The generator comprises a cylindrical duct 30 which in the illustrated embodiment is secured by flange 32 to a transition duct 34 mounted to helicopter nacelle 36. In this manner the weight of the smoke generator is supported by the aircraft structure and not directly by engine tailpipe 16, although it could be so supported if required in any other installation. In some installations the engine tailpipe can be utilized as the duct for the smoke generator and the necessary piping mounted thereto without the need for drilling holes through the tailpipe.

Supply line 19 from tank 20 leads to a T-connection 38 (FIG. 3) mounted by bracket 40 to the outside of duct 30 at an inboard position. From T-connection 38 the piping extends longitudinally in an outboard direction in the branches 42 and 44 positioned in close proximity to the outside surface of the duct to the mouth 46 thereof to provide a preheating of the smoke-producing fluid. At the mouth of the duct each pipe branch extends annularly and in an opposite direction around the duct periphery in a serpentine manner forming a manifold section 47. Intermediate portions of manifold piping section 47 are provided with a plurality of T-pipe connections 48 which support the piping to the duct adjacent the mouth and also provide lead-in piping to a plurality of corresponding in jection stations within the duct for discharging the fluid in a manner to be described presently. In the embodiment described 12 injection stations are utilized but it is obvious that the number of stations may vary with the type and size of the tailpipe and the engine.

' Connected to each T-connection 48 within the duct is a straight pipe 50 extending inboard from the duct mouth and supported to the inside of the ducts by brackets 52. Each pipe 50 terminates in a semicircular curved nozzle end 54 being pointed in an outboard direction toward the duct mouth so as to discharge the smoke-producing fluid in the exhaust gas flow and against the hot duct surfaces to be vaporized. As previously described, it is important that the characteristics of the smoke-producing fluid be such that it will be heated by the exhaust gases to the extent it will boil off and vaporize without reaching the flash point that would cause ignition and a serious fire problem.

Another important feature of the invention is the provisions for channelizing the smoke created at each nozzle station to prevent interference and eddy currents between adjacent injection stations and thus to maximize the volume of smoke being emitted from the generator unit. In the preferred embodiment of FIGS. 3-5 the channelizing is performed by baffles 56 made of a blank of sheet metal and fabricated in pairs by forming the metal blank into a U-shaped configuration, each leg being a baffle and extending longitudinally from duct mouth 46 to the nozzles 54. By this construction the baffles increase the structural rigidity of the duct against any bending moment without restraining expansion or contraction of the duct by the large temperature differential. The base 58 of the U-shaped metal is curved to conform to the duct to which it is welded or otherwise secured centrally each alternate station. Pipe 50 may be canted between its respective baffles so that nozzle 54 is centrally positioned.

In order to increase the smoke output from a given size generator it is necessary to increase the amount of heated surface area within the generator and to simultaneously increase the flow of fluid on the heated surfaces to a point of maximum efficiency. In the modification shown in FIG. 6 the height of baffles 60 are increased to extend for a major dimension of the duct radius but with the ends free to allow for expansion and contraction. In this modification each pair of baffles 60 are constructed of an inverted U-shaped sheet metal bank with the sides being the baffles, radially tapered toward the duct center. The free ends of the blank are provided with flanges which are secured to the duct interior by screws 62 at alternate injection stations. The inboard edge of each baffle is notched at 64 to accommodate a circular manifold pipe 66 extending around the duct medially the baffles and secured thereto by brackets 68. The inlet end 70 of the manifold extends through the duct to be connected to the piping from supply tank 20. A plurality of drilled openings 72 are provided in manifold 66 between the bafiles for the injection of the smoke-producing liquid on the duct and baffle surfaces. It should be noted that the increase in the heated surface is limited to a value which will not produce an unacceptable pressure drop across the generator that would affect engine performance.

The smoke-generating system provides a means for producing a high volume of opaque and dense smoke using inexpensive smoke-generating liquids that can be in a contaminated condition. The volume of smoke can be tailored by varying the number of nozzles, the pressure of the fluid and the surface area of the baffles. The baffles function in addition to providing the necessary heated surfaces to vaporize the smoke producing liquid and channelizing the smoke to prevent turbulence in the smoke flow and the building up of a back pressure on the engine. In addition, the baffles provide longitudinal rigidity to bending moments on the duct without restricting its expansion and contraction.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

I. In combination with an aircraft having a reaction-type thrust engine and an exhaust duct, a smoke generator comprising:

a plurality of nozzles mounted within and circumferentially spaced around the inner peripheral surface of the exhaust duct at the inlet thereof;

a source of smoke-producing fluid;

piping means for connecting the fluidsource to said nozzles;

a plurality of radially projecting baffle plates mounted to the inner duct surface and extending longitudinally and in parallel relation within the exhaust duct and between said noules;

whereby the fluid injected on the hot duct surfaces will generate smoke which flows aft longitudinally the exhaust duct, the smoke flow from each nozzle being channelled between the respective baffle plates to minimize turbulence therebetween.

2. The combination of claim 1, wherein the exhaust duct is mounted to the engine tailpipe as an extension thereof.

3. A smoke generator for use with an engine producing hot exhaust gases comprising:

a duct for exhausting said hot gases;

a source of smoke-producing fluid;

a plurality of fluid injection means mounted within and circumferentially spaced around the exhaust duct;

piping means for connecting the fluid source to said injection means;

a plurality of baffle means extending longitudinally within the exhaust duct in a parallel relation and disposed between said injection means; said baffle plates being plates mounted to the inner duct surface in a uniform disposition thereabout and extending radially into the exhaust duct toward the axis thereof;

whereby injection of the fluid on the hot surfaces within the duct will generate smoke which flows aft longitudinally the duct, the smoke flow from each injection means being channelled between said respective baffle means to minimize turbulence therebetween.

4. The smoke generator of claim 3, wherein said baffle plates extend radially inwardly a major portion of the radius of said exhaust duct and terminate short of said duct center.

5. The smoke generator of claim 3, wherein said baffle plates are fabricated from a sheet of metal into a U-shaped cross section with each leg being a bafile.

6. The smoke generator of claim 3, wherein said piping extends aft longitudinally along the outside to the exhaust end of said duct and then reverses direction to extend forward longitudinally inside said tail pipe to the injection means.

7. The smoke generator of claim 6, wherein the piping means includes a manifold portion which extends in a serpentine manner around the mouth of the exhaust duct and connects the outside portion of the piping to the inside portion of the piping.

8. The smoke generator of claim 3, wherein said exhaust duct is mounted to as an extension of an aircraft engine tailpipe.

9. The smoke generator of claim 3, wherein each baffle means comprises a U-shaped configuration having leg portions, the free ends of the leg portions being secured to the inner duct surface. 

1. In combination with an aircraft having a reaction-type thrust engine and an exhaust duct, a smoke generator comprising: a plurality of nozzles mounted within and circumferentially spaced around the inner peripheral surface of the exhaust duct at the inlet thereof; a source of smoke-producing fluid; piping means for connecting the fluid source to said nozzles; a plurality of radially projecting baffle plates mounted to the inner duct surface and extending longitudinally and in parallel relation within the exhaust duct and between said nozzles; whereby the fluid injected on the hot duct surfaces will generate smoke which flows aft longitudinally the exhaust duct, the smoke flow from each nozzle being channelled between the respective baffle plates to minimize turbulence therebetween.
 2. The combination of claim 1, wherein the exhaust duct is mounted to the engine tailpipe as an extension thereof.
 3. A smoke generator for use with an engine producing hot exhaust gases comprising: a duct for exhausting said hot gases; a source of smoke-producing fluid; a plurality of fluid injection means mounted within and circumferentially spaced around the exhaust duct; piping means for connecting the fluid source to said injection means; a plurality of baffle means extending longitudinally within the exhaust duct in a parallel relation and disposed between said injection means; said baffle plates being plates mounted to the inner duct surface in a uniform disposition thereabout and extending radially into the exhaust duct toward the axis thereof; whereby injection of the fluid on the hot surfaces within the duct will generate smoke which flows aft longitudinally the duct, the smoke flow from each injection means being channelled between said respective baffle means to minimize turbulence therebetween.
 4. The smoke generator of claim 3, wherein said baffle plates extend radially inwardly a major portion of the radius of said exhaust duct and terminate short of said duct center.
 5. The smoke genErator of claim 3, wherein said baffle plates are fabricated from a sheet of metal into a U-shaped cross section with each leg being a baffle.
 6. The smoke generator of claim 3, wherein said piping extends aft longitudinally along the outside to the exhaust end of said duct and then reverses direction to extend forward longitudinally inside said tail pipe to the injection means.
 7. The smoke generator of claim 6, wherein the piping means includes a manifold portion which extends in a serpentine manner around the mouth of the exhaust duct and connects the outside portion of the piping to the inside portion of the piping.
 8. The smoke generator of claim 3, wherein said exhaust duct is mounted to as an extension of an aircraft engine tailpipe.
 9. The smoke generator of claim 3, wherein each baffle means comprises a U-shaped configuration having leg portions, the free ends of the leg portions being secured to the inner duct surface. 